1. Field of the Invention
The present invention relates to an adjustable device, and more particularly to the adjustable device in combination with a stand to support a musical keyboard thereon.
2. Description of Related Art
With reference to FIGS. 7 and 8, a conventional adjustable device is mounted between a first stand (30) and a second stand (40) to allow the musical keyboard stand to adjust its height so that the operator is able to freely adjust the height of the keyboard stand (not shown) according to the operator's height.
The adjustable device includes a first disk (31) securely mounted on a side of the first stand (30), a second disk (41) securely mounted on a side of the second stand (40) and having multiple adjusting holes (411) defined through a peripheral edge of the second stand (40) and an adjusting rod (32) extending through the first stand (30), the first disk (31) and into the second disk (41). A spring (33) is mounted around the adjusting rod (32) and abutted between two opposite inner faces of the first stand (30).
When the adjustable device is in application to adjust the relative position of the first stand (30) to the second stand (40), the user is able to pull a knob (34) formed on a free end of the adjusting rod (32) extending out of the first stand (30) to allow the first stand (30) to be freely pivoted relative to the second stand (40) so as to adjust the height of the musical keyboard stand. When the height of the musical keyboard stand is determined, the operator is able to let go the knob (34) to allow the free end of the adjusting rod (32) to extend into one of the adjusting holes (411) of the second disk (41). Thereafter, the relative position between the first stand (30) and the second disk (40) is fixed. Although the adjustment of the musical keyboard stand is able to be accomplished via the conventional adjustable device, the operator will have to hold either one of the first or the second stand (30,40) with one hand and the knob (34) with the other hand, which is quite inconvenient to the operator.
In order obviate the foregoing shortcoming, a different adjustable device is introduced to the market.
With reference to FIGS. 9 and 10, a second conventional adjustable device is shown and includes a first disk securely mounted on a first stand (both the first disk and the first stand are not shown for brevity) and a second disk (51) mounted on the second stand (50).
The first disk has a blocking head (53) pivotally mounted on a side of the first disk and a resilient element (54), i.e. a spring, having a first end securely engaged with a side face of the first disk and a second end abutting a side face of the blocking head (53) to urge a free end of the blocking head (53) to pivot toward the center of the first disk.
The second disk (51) has a notched disk (52) securely mounted on a center of the second disk and having a first stop (521) and a second stop (522) spatially formed on a side face of the notched disk (52) and an abutting bar (55) pivotally mounted on the notched disk (52) and having a free end engaging with a side face of the blocking head (53).
It is noted that when the musical keyboard stand is folded, the blocking head (53) abuts the free end of the abutting bar (55) which is stopped by the first stop (521). When the operator is adjusting the first stand and the second stand (50) by enlarging the relative angle between the first stand and the second stand (50), due to the abutting force from the resilient element (54), the blocking head (53) is forced by the resilient element (54) to urge the free end of the abutting bar (55). Therefore, when the relative angle between the first stand and the second stand increases, the abutting bar (55) moves along the blocking head (53) until the abutting bar (55) is stopped by the second stop (522). Then after the blocking head (53) separates the abutting bar (55), the free end of the blocking head (53) falls into the positioning tooth (523) of the notched disk (52) where the relative angle between the first stand and the second stand is maximum. The free end of the blocking head (53) is configured in such a way that the free end of the blocking head (53) is easy to fall into and away from any one of the teeth of the notched disk (52). Therefore, the operator is able to step by step adjusts the relative angle between the first stand and the second stand (50) until the abutting bar (55) is stopped by the first stop (521) where continuous moving the first stand relative to the second stand (50) allows the free end of the abutting bar (55) to be abutted by the blocking head (53) again. The single-handed operating mechanism does solve the inconvenience from the conventional adjustable device to quickly and conveniently adjust the relative between the two stand. However, the teeth is becoming worn as the time of using the adjustable device lasts and the resilience of the resilient element (54) becomes weaker and weaker due to fatigue. The conventional adjustable device still can not fulfill the requirements.
To overcome the shortcomings, the present invention tends to provide an improved adjustable device to mitigate the aforementioned problems.